Question: Omar starts counting at 21, and he counts by fives. If 21 is the 1st number that Omar counts. what is the 9th number that he counts?
Answer: What is the first number that he counts? $21$ What is the second number that he counts? $\begin{align*}&21 + 5 \\ &= 26\end{align*}$ What is the third number that he counts? $\begin{align*}&21 + 5 + 5 \\ &= 21 + (2 \times 5) \\ &= 31\end{align*}$ What is the 9th number that he counts? $\begin{align*}&21 + (8\times5) \\ &= 21 + 40 \\ &= 61\end{align*}$